Credit cards, for instance, are not required but extremely useful. For instance, my recollection is that when booking hotels or rental cars with a debit card they will put a hold on your account for collateral. This could be a problem if you're living paycheck to paycheck. If you have a credit card, you may get a hold as well

but this is just reducing the amount of available credit. Functionally this is the same, if you have enough money, but if you're living on the edge and your rent money is in your checking account, this is pretty unfortunate in the case if a debit card.

Additionally, credit cards offer consumer protections, including chargebacks. My understanding is that debit charges are much more difficult to dispute.

And, in the US, for many people not in urban centers, owning a car is essential for life/work. Quick Google search claims, in relation to savings, "The median balance for American households is $5,300." So if your car bites the dust, buying a new (used) car may not be possible without a loan.

You're right though, it's certainly not literally required.